Systems for wireless energy transmission by means of coils (magnetic field) depend, as regards to their efficiency, heavily on the correct alignment and hence sufficient coupling of a transmitter and receiver coil. Even small deviations from the ideal position have a strong effect on the obtainable signal strength at the receiver and on the system efficiency.
Currently, several approaches exist for ensuring exact positioning. Mechanical fixing of the coil by means of housing shape or magnets, whereby primary and secondary coils are forced to the correct position, is known. Further, one-sided usage of a coil array is known which is optimally wired according to the position of the other transmission side. Further, moveable coils on a transmission side are known, which are guided to the optimum position by measuring the coupling between two coils. Above that, specific coil geometries are known, which allow a wider field distribution and hence more position-tolerant positioning.
However, the above-described approaches for positioning coils are either very expensive to implement or not suitable for positioning mobile coils.